This application claims the priority benefit of Japanese application serial no. 2001-284160, filed on Sep. 18, 2001 and 2002-234545, filed on Aug. 12, 2002.
1. Field of the Invention
This invention relates to a duct fan unit which is used for ventilating as a cooling device in various machines wherein a case thereof receives heat generation members such as a motor, a coil and a heater etc.
2. Description of the Related Art
In order to prevent temperature buildup inside a case due to continuous heat generation from the heat generation members that are disposed inside the case, such as a motor, a coil, a heater and a heat generation circuit etc., in an image forming apparatus, a communication equipment, other electrical equipment or various mechanism, a fan is used. The fan ventilates the heat generation member by removing the air inside the case to the outside. Thus the heat generated around the heat generation members can be radiated to outside.
It is well known that a fan and a duct are assembled to form a duct fan unit to achieve the function described above. FIG. 2 is a perspective view showing disassembling of a conventional duct fan unit. The duct 1 is generally made of resin. The duct 1 is disposed at a predetermined location inside a case containing a heat generation unit. The duct 1 is designed into a shape suitable for influx and exhaust of air. A fan 5 is embedded and fixed onto the inner wall of an opening 1a at one end of the duct 1. The other end 1b of the duct 1 is attached to a vent hole set on a case (not shown). The fan 5 comprises a motor (not shown) disposed inside the outer frame 6 and blades 7 driven by the motor to rotate. In this example, the fan 5 is fixed onto the duct 1 as described below. Screw receivers 2 are for example are set on four corners of the duct 1, and through holes 6a corresponding to these screw receivers 2 are set on the outer frame 6 of the fan 5. Long screws 8 are driven through the through holes 6a and into the screw receivers 2 in order to fix the fan 5 onto the duct 1.
However, in the conventional duct fan unit, because the screws 8 are used to fix the fan 5 inside the duct 1, not only the assembly operation but also the disassembling operation is complicated. Thus both assembly and disassembly operations becomes very inconvenient and therefore cannot be effective.
The Japanese Laid-Open publication no. 2000-22375 discloses a structure in which the fan unit can be easily replaced when the fan unit is out of order. The structure is shown as FIGS. 3A and 3B, a resilient plate 42 and an engaging plate 43 are used to fix the fan unit 41 onto the fixing portion 44. The resilient plate 42 is in contact with one side of the fan unit 41 and the resilient plate 42 presses the fan unit 41 to one side. The engaging plate 43 disposed opposite to the resilient plate 42 is latched to the fan unit 41 and the engaging plate 43 fixes the fan unit 41 at a predetermined position. Structure members for limiting the positions of the resilient plate 42 or the engaging plate 43 and the fan unit 41, such as limiting portions 45, 46 etc. are integrally formed with the duct frame 40 that receives a heat generation unit. Furthermore, the resilient plate 42 and the engaging plate 43 are perpendicular to the flow passage of the cooling air of the fan unit 41.
In spite of the simplified assembly and disassembly operations facilitated by the structure disclosed in the Japanese Laid-Open publication no. 2000-22375, however, it can be understood from the drawings that the structure is very complicated. Therefore, the manufacture cost becomes high.
Another Japanese Laid-Open publication no. He7-92862 as shown in FIG. 4, discloses a structure comprising a duct which is assembled by a pair of duct constructing members 51, 52 for ventilating air and a fan 53 that is clamped and supported within the duct by the pair of duct constructing members 51, 52. The plane of engagement of the pair of duct constructing members 51, 52 of the duct is substantially along the air flow direction. When assembling, the fan 53 is positioned and clamped by using guide ribs 56, 57 that are formed as an individual pair of ribs on the inner wall of the duct constructing members 51, 52, so that a duct is formed, then the duct constructing members 51, 52 are secured by the fastening screws. A duct case 55 where an ozone filter 54 is inserted to an end of the duct is fixed by screws. Each guide rib 56, 57 is constructed by a pair of rib portions protruding perpendicular with respect to air flow direction.
In spite of the disassembly operation of the fan 53 from the duct facilitated by the structure disclosed in the Japanese Laid-Open publication no. He7-92862, the problem resulting from using the pair of guide ribs 56, 57 to fix the fan 53 to a fixed position the fan 53 inside the duct occurs. When assembling, if the direction of the guide ribs 56, 57 are not perpendicular to the air flow direction, the fan 53 cannot be clamped under the desired condition. Further, the duct constructing members 51, 52 cannot be correctly assembled to construct the duct. Therefore, the formation of the duct constructing members 51, 52 which are generally made of resin is required to be constructed under a precision conditions and thus the cost thereof is high. Furthermore, when the position of the guide ribs 56, 57 gets slightly changed, attempts to assemble the fan 53 and the duct constructing members 51, 52 by force may break the duct constructing members 51, 52.
One object of the present invention is to provide a duct fan unit wherein the fan is installed inside a duct without those inconveniences described above. The structure of the duct fan unit is simpler and the operation of detaching the fan is easy and the manufacture cost can be decreased.
For solving the problems described above, another object of the present invention is to provide a duct fan unit wherein the fan is installed inside a duct to solve the inconvenience of detaching the fan as experienced by fixing the fan to the conventional duct using screws.
In accordance with the above objects and other advantages of the present invention, a structure of a duct fan unit is provided. The duct fan unit comprises a duct, at least a fan, at least a guide portion and at least a protrusion portion. The duct is divided into a pair of duct constructing members to allow air to pass through. The fan is clamped by the pair of duct constructing members and supported inside the duct, wherein a division direction of the duct is substantially along an air flow direction created by the fan. The guide portion is disposed at an inner wall of one of the duct constructing members to limit an installation position of the fan inside the duct. The guide portion extends from the inner wall of the duct member in a shape of a rib perpendicular to the division direction. The protrusion portion is disposed at an inner wall of the other duct constructing member to make contact with an outer wall of the fan and to resiliently press the fan towards a side of the duct constructing member. The protrusion portion protrudes towards a direction perpendicular to the division direction.
According to an aspect of the present invention, at a side wall where the protrusion portion is formed, a portion surrounding the protrusion portion is notched to form at least a pair of openings facing to each other.
According to another aspect of the present invention, the pair of openings is a pair of slots.
According to another aspect of the present invention, the duct fan unit comprises a duct and a fan. The duct allows air to pass through and the duct is divided into two duct constructing members along an axial direction of the duct. The fan is embedded on an inner wall of the duct. The fan is clamped by the two duct constructing members and an outer wall of the fan is pressed inward and supported by the inner wall of the duct
According to another aspect of the present invention, the duct constructing members comprise a connecting portion respectively formed on the ends of the duct constructing members with the connection portion of one duct constructing member facing the connecting portion of the other duct constructing member, and the two duct constructing members are detachably latched to each other through the connecting portion. The connecting portion comprise a connecting claw set at one of the duct constructing member and a receiving portion set at the other duct constructing member for receiving the connecting claw.
According to another aspect of the present invention, at least one duct constructing member further comprises a resilient portion disposed at an inner wall of the duct constructing member and the resilient portion is in contact with an outer wall of the fan, and the fan is resiliently pressed inward by the resilient portion.
Additionally, the fan mentioned in the present invention is not restricted to only the fan itself but other things assembled with fan, for example like the filter etc. disclosed in the Japanese Laid-Open publication no. 7-92862 are also involved.